Laryngoscopic View after Application of Manual In-Line Stabilization - A Comparison with Early Morning Sniffing Position in the Same Patient.

Background: The application of manual in-line stabilization (MILS) for minimizing spinal cord injury is known to increase difficulty in airway management.

Aim: The study aims to assess the change in Modified Cormack-Lehane (CL) laryngoscopic view with the application of MILS from the early morning sniffing position (EMSP) in adult patients.

Setting and design: This was a prospective, interventional, self-controlled study conducted on 220 patients aged 18-65 years, belonging to the American Society of Anesthesiologists Physical Status Class I or II, having a normal airway, and scheduled for elective surgery under general anesthesia.

Materials and methods: After inducing general anesthesia, MILS was applied to the patient's neck, and a Modified CL view of the vocal cords was recorded under direct laryngoscopy. The view was again noted after applying backward-upward-rightward pressure (BURP). MILS and BURP were released. The view was obtained again with and without BURP in EMSP.

Statistical analysis: Normality of data was tested by Kolmogorov-Smirnov test. Wilcoxon ranked-sum test for quantitative variables and Chi-square test for qualitative variables were used.

Results: On application of MILS, the majority of patients had Modified CL Grade 3a (121 patients) and 3b (53 patients) views. The majority of patients had Modified CL Grade 1 (114 patients) and 2a (71 patients) views on placing in EMSP. These findings were statistically significant (P < 0.0001). Consequent to the placement of BURP upon MILS, patients with lower CL Grade views (2b: 101 patients) were significantly higher (P < 0.0001) in comparison with MILS alone.

Conclusion: In patients with a normal airway, MILS leads to a significantly greater incidence of higher grades of laryngoscopic views in comparison to EMSP. Use of BURP after MILS causes significantly less incidence of higher grades of laryngoscopic view when compared with MILS alone. All patients requiring MILS should be considered to be a difficult airway, and hence, preparation should be done accordingly.